Full Idea
I regard you all as relatives - by nature, not by convention. By nature like is akin to like, but convention is a tyrant over humankind and often constrains people to act contrary to nature.
Clarification
'Convention' is the Greek word 'nomos', which also translates as 'law'
Gist of Idea
By nature people are close to one another, but culture drives them apart
Source
Hippias (fragments/reports [c.430 BCE]), quoted by Plato - Protagoras 337c8
Book Reference
'The First Philosophers', ed/tr. Waterfield,Robin [OUP 2000], p.255